Due to advances in computer technology, there has been an ever-increasing need for data storage in data processing networks. In a typical data processing network, there has been an increase in the number of volumes of data storage and an increase in the number of hosts needing access to the volumes. This has been especially true for networks of work stations. Not only have a greater number of workstations been added to the typical network, but also the increase in data processing capabilities of a typical workstation has required more data storage per workstation for enhanced graphics and video applications.
Fortunately for computer users, the cost of data storage has continued to decrease at a rate approximating the increase in need for storage. For example, economical and reliable data storage in a data network can be provided by a storage subsystem including a Redundant Array of Independent Disks (RAID). Presently it is practical to provide a single data storage subsystem with up to 20 terabytes (TB) of storage, or approximately 4000 logical volumes, using magnetic disk drives each having a storage capacity of 46 gigabytes.
Unfortunately for network administrators, the development of services for storage management has lagged behind the increase in storage to be managed. Consequently, the cost of storage management has become relatively more significant. More troubling is the difficulty of maintaining the same level of management service as the amount of storage increases. For example, users are accustomed to being provided with backup and restore services for their data that is stored on the network. Users are encouraged to store their data on the network so that it can be shared by other authorized users and maintained in a cost-effective manner in accordance with corporate document retention policies. However, data stored on the network is always subject to some chance of loss due to a severe failure of the data storage system. Backup and restore services are a conventional way of reducing the impact of data loss from the network storage. To be effective, however, the data should be backed up frequently, and the data should be restored rapidly from backup after the storage system failure. As the amount of storage on the network increases, it is more difficult to maintain the frequency of the data backups, and to restore the data rapidly after a storage system failure.